Algal symbiosis and its recognition in the fossil record.

Abstract

Reviews the nature of algal symbionts, the phyletic distribution of hosts of algal symbionts, and the geographical and ecological distribution of algal symbiosis (generally restricted to shallow waters free from turbidity and with no strong seasonal fluctuations in light intensity, and commonly developed in nutrient-poor tropical reefs and in the surface layers of blue-water tropical pelagic environments). Evolution of algal symbiosis has probably been a rather rare event, but once established symbiosis probably spread at a geologically rapid rate among any suitably preadapted host organisms. Characters associated with symbiosis are mooted, and the means of recognising algal symbiosis in the fossil record are indicated. Case studies include discussion of the feeding mechanism of the Richthofeniacea, and examination of symbiosis in the Richthofeniacea, Teguliferinidae and Lyttoniacea. The origins of symbiosis in the Brachyopoda are also suggested.-P.J.Jarvis